Q1. [4]
Asexual reproduction involves a single parent to produce offsprings without the formation of gametes. It occurs by the following ways : Fission, Budding, Fragmentation, Spore formation and Regeneration. In one of the methods like regeneration, Planaria A is cut horizontally into three pieces – L, M and N and Planaria B is cut vertically into two equal halves – O and P.
Read the source and answer the sub-parts that follow.
- (a) Which of the cut pieces of the two Planaria could regenerate to form a complete organism ? [1]
- (b) Give an example of another organism which follows the same mode of reproduction as Planaria. [1]
- (c) What is the meaning of 'development' in regeneration ? [2]
Previously asked in CBSE board exam
2024 31/2/1 Q38
Generated by claude-sonnet-4-6 · 2026-06-15 06:45 · grounding stimulus
Model Answer
(a) All pieces of Planaria A (L, M, and N) and both halves of Planaria B (O and P) can regenerate into complete organisms, as Planaria has the ability to regenerate from any cut piece.
(b) Hydra is another organism that follows the same mode of reproduction (regeneration) as Planaria.
(c) 'Development' in regeneration means that the specialised cells present in the cut piece multiply and form a mass of cells. These cells then differentiate and develop into various cell types and tissues, gradually organising into a complete new organism with all its body parts.
Source: Chapter – How do Organisms Reproduce?, Section – Regeneration
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Explanation
- (a) In Planaria, every cut piece can regenerate — examiners expect students to name all pieces (L, M, N, O, P).
- (b) Hydra is the standard textbook example alongside Planaria for regeneration.
- (c) The 2-mark answer must cover two steps: (i) cell multiplication forming a cell mass, and (ii) differentiation/development into a complete organism. Missing either step costs a mark.
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